Electric switch



0d. 1955 J. D. BUCHANAN ET AL 2,767,276

ELECTRIC SWITCH Filed June 18, 1954 2 Sheets-Sheet 1 JD. Baa/4W4, C421.E1 MON/V1674, 5'2.

I N V EN TORS.

06L 1956 J. D. BUCHANAN ET AL 2,767,276

ELECTRIC SWITCH Filed June 18, 1954 2 SheetS Sheet 2 IN VEN TORS.

' v ,v 45 f5 United States Patent ELECTRIC SWITCH J. D. Buchanan andCarl Earnest Monnich, Sn, Burbank, Califi; said Monnich assignor to saidBuchanan Application June 18, 1954, Serial No. 437,619

8 Claims. (Cl. 200-82) The invention relates to an electric switch andmore particularly to a hydraulic pressure operated switch for operatinga signal or for connecting auxiliary equipment such as a pump when thefluid pressure reaches a certain low value.

As described in co-pending application, Serial No. 286,991, filed May 9,1952, now Patent No. 2,736,778, by one of the joint inventors herein,namely, J. D. Buchanan, for Hydraulic Pressure Operated Switch, it isexplained that such a switch is useful for providing a signal light inthe pilots position in an airplane to show whether the oil pressure ishigh enough such as 3000 lbs. p. s. i. to operate the hydraulic motorsor pistons which operate the various components of an airplane.

The above mentioned co-pending application discloses and claims a switchof the character described wherein a micro-switch is arranged at oneside of a hydraulic plunger with an intervening switch operating elementwhich is cocked against the action of a spring for sudden release bysnap action into or out of operative engagement with the switch as theplunger moves in one direction or the other. The micro-switch has bothfront and back contacts and proper high oil pressure with an inwardposition of the plunger can either open or close a circuit to a signalor other device depending on how the switch is connected in the circuit.In the case of a signal when the oil pressure has a lower value such as2700 lbs. p. s. i. the switch actuates a signal device to show the pilotthat the oil pressure is below normal.

While the switch of the present invention is generally similar to theswitch of the above application, the present invention is an improvementthereon in a number of respects, principally regarding ease ofmanufacture, reduction in the number of working parts and ease of adjustment of the micro-switch casing with respect to its operatingelement and also the ease of adjustment of the switch operating elementin relation to both the hydraulic plunger and the micro-switch andadjustment of the snap acting connection between the plunger and theswitch operating element to adjust the differential between the high andlow pressure operating points of the switch, and more particularly toadjust the low operating point of the switch to different values forsubstantially the same or other high pressure operating values.

In the former application, the casing was provided with a'bore open atits opposite ends for the hydraulic plunger and its spring, whereas thepresent invention provides a single dead-end bore and provides a morecompact arrangement by housing the plunger spring in a spring barrelwhich actuates the switch operating member.

Also in the former application, the switch operating element wasprovided with a cam surface which acted on a fixed cam follower to raisethe switch operating element for sudden release into operatingengagement with the switch while another cam surface on the switchoperating element escaped an abutment on the plunger, this abutment orsear element serving to cock the switch operating element against theaction of a spring. The present ICC invention provides a furtherimprovement in dispensing with the first mentioned cam on the switchoperating element and in providing inter-engaging transverse or searfaces on the plunger and on the switch operating element for cocking theswitch operating element against the action of a spring for suddenrelease when the sear on the switch operating element escapes itscooperating sear on the plunger, whereupon the switch operating element,as the plunger moves inwardly, comes to rest on an elevated portion ofthe plunger surface, to support the switch operating element in positionto operate the switch to its alternate position. When the pressuredrops, the switch operating element snaps back to a lower position tooperate the switch to its other position. In other words, the plunger isprovided with surfaces at different elevations to support the switchoperating element into or out of operative engagement with the switch.

The present invention is also an improvement of the above mentionedapplication in another respect, namely, in the former case, when theplunger was in, due to high pressure, the switch operating member was inelevated position, the present invention being an improvement byarranging the switch operating element on a sliding pivot so that whenthe plunger is in, with one end of the switch operating elementelevated, its other end which operates the switch, is lowered,preferably to open the switch. The ease of adjustment above mentioned isprovided by mounting the micro-switch on a bracket so that it can beadjusted with respect to the switch operating element, and the latter isadjusted by arranging its pivot eccentrically on a rotatable mount suchas a screw, so that the screw can be rotated to move the switchoperating element transversely to the line of travel of the plunger toadjust the amount of engagement of the scars with each other to changethe above mentioned differential between the high and low operatingpoints of the switch pressure. While this eccentric adjustment alsoresults in shifting the sear on the switch operating element lengthwiseof the travel of the plunger, which is not desired, this can becompensated for by adding or removing a shim at one end of the plungerspring to adjust the tension on the plunger spring to the same value ithad before such an adjustment of the pivot.

The invention also provides an improved piston with ring seal andpacking to prevent leakage which seals against leakage at the highpressure employed whereas the frictional load or hysteresis is lowwhereby the switch operates within close limits.

For further details of the invention reference may be made to thedrawings wherein Fig. l is a sectional view of an electric switchaccording to the present invention.

Fig. 2 is a sectional view on line 22 of Fig. 1 looking in the directionof the arrows.

Fig. 3 is a partial sectional view on line 33 of Fig. 1.

Figs. 4 and 5 are sectional views corresponding to Fig. l, with partsbroken away, showing the plunger and switch operating element indifferent operating positions.

Fig. 6 is a view corresponding to Fig. 1 with parts broken away showingthe eccentric adjusted to a raised position, with the plunger in anouter position.

Fig. 7 is a view corresponding to Fig. 6, with the same eccentricadjustment a Fig. 6 and showing the switch operating member in itsalternate position with the plunger in an inner position.

Referring in detail to the drawings, the switch 1 comprises a casing 2having side walls 3, 4 and 5 and a removable cover 6, which define aswitch chamber 7. Chamber 7 has a back wall 8 having bosses 9 and 10 forbolts 11 and 12 which pass through the casing 13 of a well knownmicro-switch 14 whereas switch 14 has casing members held together by arivet 15 and this switch is mounted on a base plate 16 by means of abolt 17. Plate 16 has an arcuate slot 18 concentric with bolt 12 so thatby loosening these bolts, the plate 16 can be swung about the axis ofbolt '12 to adjust the position of the switch casing 13. Switch 14 has aswitch operating element or button 26 which in the position shownconnects the spring contact 21, in circuit with the terminal 22, to thecontact 23 connected to terminal v24, while in its alternate positionwhen the button 2% is pushed in, contact 21 engages the alternatecontact 25 connected to terniinal26. As the button 2% is operated, theleaf spring 27 snaps the contact 21 to oneposition or the other, theswitch 14 itself being well known and forming no part of the presentinvention.

One side of switch chamber 7 has an opening 23 closed by an electricalreceptacle 29 held in positionby screws like 39. The receptacle 29 isfluid tight and has a seal 31. In fact, the whole interior of the casing2 is fluid tight and the air is exhausted through an opening 32, seeFig. 3, and the casing is then filled with an inert gas such asnitrogen, whereupon the opening 32 is sealed with the screw 33 having aseal in the form of an O-ring 34 and a sealing compound 19 such asvarnish.

The electrical receptacle 2? is connected to some or all of theterminals 22, 24, 26 as desired, by means of wires not shown in theswitch chamber 7.

The switch chamber 7 opens into a dead end cylinder 35 closed at itsright hand end as seen in Fig. 1 and open at its left hand end throughwhich is fitted an end cap 36. Cap 36 has a seal 37 and an inlet 38 forthe fluid pressure'such as hydraulic oil. The inlet 38 communicates witha double piston 39 which slides in a cylinder 49. The intermediateportion of the piston 32? is of reduced diameter as shown at 41 andprovided with a seal such as ring seal 42 and oil resisting sealingrings 43.

The inner end of piston 3? has an enlarged thin head 44 larger than thecylinder 46 which prevents the piston 39 from falling out when the cap36 is removed and piston 39 inserted in the inner end of cylinder 40, aswell as fitting against the outer end 64 of the hollow plunger 45 totransmit the force of'piston 35 to the plunger 45. The inward movementof piston 39 due to fluid pressure in inlet 38 is opposed by spring 46.While various sizes of the switch parts and springs of various strengthsmay be used, by way of example, Fig. 1 shows in double scale one form ofinvention which has been constructed and used, the plunger spring 46having a force of 460 lbs. per inch.

The casing 2 is provided with apertures for mounting bolts47, 48, tomount the switch 1 on a panel or the like. The inner end of cap 36 has aflat circular rim 67 which serves as a stop for the outer end 64 of theplunger 45, the inward movement of plunger 45 being limited by the wall4 of casing 2.

The switch chamber 7' opens into the cylinder 35 so that the plunger 45can operate a hammer or switch operating member which operates theswitch button 20. The member 519 has an open elongated slot 51 whichrotatably and slidingly fits on an eccentric 52 to support the member 56for pivotal movement about the axis of eccentric 52 and also fortransverse movement toward and away from the switch button '26.Eccentric 52 as shown in Fig. 2 may comprise the intermediate portion ofa screw 53 which fits in a threaded bore 49 being held in adjustedposition by a lock screw 55. The position ofeccentric 52 can be adjustedby removing the lock screw '55 and by applying a screw driver to thekerf 56 in the head of screw 53. Figs. 1, 2, 4 and'S al show eccentric52 in the same position of adjustment, namely with the eccentric in itsclosest position to the plunger 45, that is with its center on avertical through the center of screw 53 as seen in Figs. 1, 4 and 5. Thereason for Arm 65 has an 1 end 57 by the higher level or land 60 of theplunger as shown in Fig. 5, the inner end 58 of arm 54 at this timeriding on the elongated plunger surface 59 of lower level. The arm 54 isurged into supporting relation with the plunger 45 by means of a spring61 which centers a lug 62 on the arm 54, and bears against the undersideof the switch casing 13. Betweenthe high and low levels 59 and 6'.) ofthe plunger 45 is a transverse surface 68, that is it extendstransversely to the line of travel of plunger 45. The levels 59 and andsurface 63 thus form an inwardly facing shoulder acting as an escapementcatch or sear which slidingly fits on, catches and at times releases anoutwardly facing transverse surface 69 at the outer end 57 of the arm 54of the switch operating member 5%. The switch operating arm 54 on itsunderside has an elongated surface 76 which is shorter than the lowerlevel 59 and is adapted to rest on the plunger v'ith'the inner end 58 ofarm 54 on the lower level 59 while the outer end 57 of that arm isresting on the high level or land 60, with the arm 65 and its surface 66in elevated position operating the switch button 20 to one of itspositions. At other times, the switch operating arm 54 is adapted torest on the lower level 59, as shown in Fig. 1, without being tilted upat its outer end, the arm 65 at this time being in a retracted positionso that the switch button 20 is new extended to its alternate position.The switch operating member 50 is shifted from one of these positions asshown in Fig. 5 to the other position as shown in Fig. 1, as the plunger45 moves in and out, as follows.

When the plunger 45 is in an outer position as shown in Fig. 1, the arm54 is on the lower level 59, not supported by the higher level 60. Atthis time, the eccentric 52 has such a position in relation to the arm54 that the arm 54 does not lie exactly flat on the lower level surface59 but instead is tilted up at its outer end by a very slight angle asshown at 71 in Fig. 1. As the fluid pressure in inlet 38 reaches acertain value sufficient to overcome spring 46, the plunger 45 movesinwardly and its face 68 exerts a thrust on the face 69, causing themember 50 to rotate counter clockwise, or cock against the action ofspring 61 as shown in Fig. 4, the switch button 20 being unaffected bythis cocking movement. A slight additional inward movement of plunger 45beyond the position shown in Fig. 4, causes the surface 69 to escape theplunger surface 68 at a unique plunger position to bring the parts tothe position shown in Fig. 5 as previously described, with switch button20 actuated to its alternate position. For higher values of the inletpressure, the plunger 45 can move inwardly beyond the position shown inFig. 5 without affecting the operation of the switch, until the wall 4acts as a stop to limit the plunger movement.

The differential between the high and low pressure operating points ofthe switch depends on the travel of plunger 45 from the position shownin Fig. 1 to the position just beyond the position shown in Fig. 4 asillustrated in Fig. 5. In other words, it is substantially the overlapof the surface 70 at the end 57 of the operating member 50 with thehigher level surface 60. This differential may be adjusted tosmallervalues by adjusting the eccentric 52 to elevate the axis about which theoperating member pivots and to position the operating member 50 so thatin its lowermost position, its transverse face '69 only partiallyoverlaps the plunger transverse surface 68. This is shown in Fig. 6wherein the eccentric '52 is illustrated as having been rotatedcounterclockwise with the result that in its lowest position, the face69 only overlaps about one-half of the plunger surface'68. In this case,the plunger 45 moves "inwardly a lesser distance than before in order toraise the member 60 to the point where its surface .69 will escape theplunger surface 68 and hence the differential between the high and lowpressure operating points of the switch is less than it was before. Fig.7 illustrates the same eccentric adjustment as in Fig. 6 and shows thatafter escapement, the overlap of the under surface 70 of member 50 withthe higher level plunger surface 60 is about one-half the amount that itwas before. Other values of this differential may be obtained byadjusting the eccentric 52 to other positions. The adjustment ofeccentric 52 may necessitate readjustment of the position of button 20with respect to arm 65 so that button 20 will be in its idle positionwhen arm 65 of operating member 50 is in its lowest position as shown inFig. 6. This adjustment is readily accomplished by adjusting the baseplate 16 of the switch as previously described.

When the eccentric S2 is moved from the position shown in Fig. 1 toelevate the pivot axis of member 50 and change the differential aspreviously described, this adjustment also shifts member 50 lengthwiseof plunger 45 and changes slightly the high and low pressures at whichmember 50 operates. In cases where this is undesirable, this can becompensated for by adding one or more shims as illustrated at 72 in Fig.1, between the outer end of spring 46 and the head or end 64 of theplunger. The high pressure at which the switch operates can thus be keptat the same value as it had before the adjustment of eccentric 52 ifdesired. In some cases this compensation can be accomplished by rotatingeccentric 52 through an angle 180 from the position shown. Due to thespecial requirements for this particular switch device, it is notpossible to have anything project beyond the wall 4 of the casing, andhence the means for adjusting the tension of spring 46 has beenillustrated as one or more shims 72, although other means for adjustingthe tension of spring 46 may be employed in other situations.

Various other modifications may be made in the invention withoutdeparting from the spirit of the following claims.

We claim:

1. A switch device comprising a switch having an operating element, aswitch operating member therefor, means supporting said switch operatingmember for movement to one position to actuate said switch to oneposition or to another position to actuate said switch to an alternateposition, a reciprocating hydraulic plunger having surfaces at differentlevels for supporting said switch operating member in one or the otherof its said positions, spring means urging said switch operating memberin supporting engagement with said plunger, said plunger having aninwardly facing shoulder acting as an escapement catch, and saidoperating member having a coacting outwardly facing transverse surfacefor cocking said operating member against the action of said springmeans when said plunger moves inwardly, said operating member having aswitch operating arm which is inefiective to operate said switch elementduring said cocking, said transverse surface escaping said shoulder onfurther inward movement of said plunger to a unique position with saidswitch operating member supported on a higher one of said levels inposition to operate said switch element to an alternate position.

2. A switch device according to claim 1, said means supporting saidswitch operating member comprising a screw having an eccentric bearingand said switch operating member having an elongated bearing surfacetherefor for pivotal movement of said switch operating member forengagement and disengagement of said transverse surfaces as well asmovement of said switch operating member toward and away from saidswitch operating element, said eccentric bearing comprising means foradjusting the transverse position of said switch operating member andits transverse surface with respect to said shoulder of said plunger.

3. An electric switch comprising a casing having a hollow hydraulicplunger having a piston, a spring in said plunger opposing said piston,a micro-switch in said casing at one side of said plunger, saidmicro-switch having an operating element having alternate operatingpositions, a switch operating member between said switch operatingelement and said plunger and having portions in operative relation toeach thereof, means on said casing movably supporting said operatingmember, spring means maintaining said switch operating member insupporting relation on said plunger when said plunger is in or out, andmeans for actuating said switch operating element to one or the other ofits said positions with a snap action, said actuating means comprisingcoacting escapement shoulders on said plunger and on said switchoperating member for extending or retracting said switch operatingmember against the action of said spring means on escapement of saidshoulders.

4. A switch device comprising a plunger, a switch having an operatingelement at one side of said plunger, a pivotal support, a switchoperating member having a cam arm having a slide bearing on said supportfor pivotal movement thereon and for lateral movement of said cam arminto and out of engagement with said switch operating element, saidoperating member having another arm having an end and an intermediateportion having an outwardly facing transverse surface, a spring urgingsaid other arm towards said plunger, said plunger having an inwardlyfacing shoulder acting as an escapement catch, said plunger having anouter idle position wherein said shoulder is removed from the transversepath of said other arm and with said spring urging said end of saidother arm into supporting relation with said plunger and urging said camarm to idle position out of operating engagement with said operatingelement and with said shoulder facing said transverse surface, saidplunger having an intermediate range of inward movement with its saidshoulder engaging said transverse surface and cocking said operatingmember against the action of said spring by pivotally moving saidoperating member while said cam arm remains out of operating engagementwith said operating element, said plunger having a further inwardposition with said transverse surface escaped from and said intermediatearm portion laterally resting on said shoulder and with said end of saidother arm engaging said plunger and with said cam arm laterallydisplaced into operating relation with said operating element.

5. A switch device according to claim 4, said plunger being hollow andhaving a hydraulic piston, and a spring in said plunger opposing saidpiston.

6. A switch device according to claim 4, said plunger being hollow andhaving a hydraulic piston, a spring in said plunger opposing saidpiston, said pivotal support comprising means for adjusting the overlapof said transverse surface with said shoulder when said plunger is insaid idle position to adjust the differential between the high and lowpressure operating positions of said switch, and means for supplyingfluid pressure to operate said plunger.

7. A switch device comprising a casing having a plunger, a switch havingan operating element at one side of said plunger, an eccentric on saidcasing, a switch operating member having a transverse slot slidably andpivotally fitting said eccentric, said operating member having oneportion extending into or out of operating engagement with saidoperating element on transverse movement of said one portion towards oraway from said operating element respectively, a spring urging saidoperating member towards said plunger, said operating member havingpivotal cocking movement on said eccentric against the action of saidspring with said one portion out of operating engagement with saidoperating element, cooperating scars on said plunger and on saidoperating member for producing said cocking movement and subsequentrelease of said operating member on inward movement of said plunger,said plunger sear having 'a land isupporting'said one portion inoperating engagementwith said switch element on said release when said.plunger sear escapes said other sear on inward movement of said plunger,and means to adjust said eccentric to adjust the overlap of said'sears.

8. A switch device comprising a casing having a plunger, aswitch havingan operating element at one side of said plunger, a pivot on saidcasing, a switch operating member having a transverse slot slidably andpivotally fitting said pivot, said operating member having one portionextending into or out of operating engagement with said operatingelement 'ontransverse movement of saidone portion towards or away fromsaid operating element respectively,'a spring urging said operatingmember toward'saidplunger, said operating member having pivotal cockingmovement on said pivot against the action of said springrwith said oneportion out of operating engagement with said operating element,cooperating sears on said plunger and on said operating member forproducing said cocking movement and subsequent release of said operatingmember on inward movement of said g plunger, said plunger sear havingraland supporting said one portion in operating engagement withsaid switchelement'on said release when said plunger sear escapes said other searon inward movement of said plunger.

References Cited in the file of this patent UNITED STATES PATENTS2,073,141 Chaney Mar. 9, 1937 2,485,074 Stevenson Oct. 18, 19462,492,261 Bordelon Dec. 27, 1949 2,504,381 Bordelon Apr. 18, 19502,507,065 Trautman May 9, 1950 2,511,271 .Kaminky et'alh June 13, 19502,529,688 'Grupp Nov. 14, 1950 2,533,559 'Chipman Dec. 12, 19502,579,172 Bordelon Dec. 18, 1951 2,666,829 Burkhard et al. Ian. 19, 19542,732,450 Stevenson Jan. 24, 1956 2,736,778 Buchanan Feb. 28, 1956

